Export Video and Audio (5.1 Mix via Audition) to Media Encoder - Video OFFLINE

I sent a sequence to Audition via Dynamic Link and did a Surround Mix on it. I have a Surcode Dolby Plus license. I then tried to export my session in Audition straight to AME using the File > Export > Export with Adobe Media Encoder. But when I do that it opens AME and starts exporting it, but the video shows as offline (red offline image). 

Any ideas why this is happening?

To get around it I'm having to mixdown the surround mix, bring that into Premiere and export from there. But I'm wondering what I'm doing wrong within Audition that the exported session is coming up with all the video OFFLINE.